powerpc/64e: Fixup oops when debug programs with CONFIG_RELOCATABLE=y

Debug interrupts can be taken during regular program or a standard
interrupt.  The EA of the instruction causing the interrupt will be kept
in DSRR0.  The kernel will check whether this value is between
[interrupt_base_book3e, __end_interrupts].  However, when the kernel is
built with CONFIG_RELOCATABLE, it can't use
LOAD_REG_IMMEDIATE(r14,interrupt_base_book3e) and
LOAD_REG_IMMEDIATE(r15,__end_interrupts), as they ignore relocation.

At the same time, r2(toc) is not usable here, so LOAD_REG_ADDR() doesn't
work either.  So we use the *name@got* to get the EV of two labels
directly.  This patch fixes the oops when we gdb a program with single-step.

Test programs test.c shows as follows:
int main(int argc, char *argv[])
	if (access("/proc/sys/kernel/perf_event_paranoid", F_OK) == -1)
		printf("Kernel doesn't have perf_event support\n");

Steps to reproduce the bug, for example:
 1) ./gdb ./test
 2) (gdb) b access
 3) (gdb) r
 4) (gdb) s

Then will trigger the oops, it looks like:
(gdb) s
Single stepping Oops: Exception in kernel mode, sig: 5 [#2]
PREEMPT CoreNet Generic
Modules linked in:
CPU: 0 PID: 1135 Comm: test Tainted: G    D    Linux (none) 4.9.5 #79
task: c000000079199580 ti: c00000007ffc4000 task.ti: c000000074064000
NIP: c00000000001a1e4 LR: 000000001000103c CTR: 000000001000100c
REGS: c00000007ffc7cf0 TRAP: 0d08   Tainted: G   D  (Linux (none) 4.9.5)
MSR: 0000000080021000 <CE,ME>  CR: 24000442  XER: 00000000
GPR00: 0000000010001274 00000000ffffeba0 00000000100ab4b0 00000000100764a4
GPR04: 0000000000000000 00000000ffffee2c 00000000ffffee54 00000000100a44c8
GPR08: 0000000000000001 0000000010070000 00000000100a0000 0000000000000001
GPR12: 000000004347432f 00000000100aa648 0000000000000000 0000000000000000
GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR24: 0000000000000000 0000000010001950 0000000010001850 0000000000000000
GPR28: 0000000000000000 00000000100000f4 0000000000000000 00000000ffffeba0
NIP [c00000000001a1e4] interrupt_base_book3e+0x1e4/0x348
LR [000000001000103c] 0x1000103c
Call Trace:
Instruction dump:
00000000 00000000 00000000 60000000 4800e600 00000000 00000000 00000000
00000000 00000000 00000000 60000000 <4800e588> 00000000 00000000 00000000

Signed-off-by: Liu Hailong <liu.hailong6@zte.com.cn>
Signed-off-by: Jiang Xuexin <jiang.xuexin@zte.com.cn>
Reviewed-by: Jiang Biao <jiang.biao2@zte.com.cn>
Reviewed-by: Liu Song <liu.song11@zte.com.cn>
Reviewed-by: Huang Jian <huang.jian@zte.com.cn>
[scottwood: cleaned up commit message]
Fixes: 1cb6e0649248 ("powerpc/book3e: support CONFIG_RELOCATABLE")
Cc: <stable@vger.kernel.org> # 4.4.x-
Signed-off-by: Scott Wood <oss@buserror.net>
1 file changed